Microstructured optical fibers (MOF) are a highly efficient support for the design and construction of sensitive and lowcost sensors. Currently, molecular imprinting is one of the promising method of MOF inner surface functionalization. Molecularly imprinted polymers (MIP) can be synthesized at MOF inner surface and intensify the selectivity and efficiency of target molecules sorption. This approach can be the base for selective sorption and detection of target molecules on a single sensor device. This paper describes MOF modification by MIP selective for bovine serum albumin (BSA). Polyaniline was used as matrix MIP polymer and was obtained by chemical oxidate polymerization of aniline in soft acid conditions. MOF transmission spectrum were used for monitoring of bonding between the protein molecules and MIP.
Microstructured waveguides with hollow core (HC-MOW) are of great interest for chemical and biological sensing. Due to the high overlap between a guiding light mode and an optical signal of analyte solution, filling of one or several fiber capillaries, such systems are able to provide strong sensitivity with respect to variations in the refractive index and the thickness of filling materials. Our approach is based on layer-by-layer assembly of oppositely charged polyelectrolytes with different molecular weights on the inner surface of HC-MOW. It was shown, the deposition of polyelectrolyte layers on the inner surface of hollow core causes a redshift in the transmission spectra. In particular, transmission shifts of up to 13 nm were detected for a multilayer polymer coating (5 bilayers).
Microstructural optical waveguides with the hollow core are actively studied as a promising support for heterogeneous immunoassay in development of new optical biosensor elements for medicine and biology. Overcoming of the limitations associated with the low sorption capacity of glass used for the waveguides production is a crucial step for this assay format. In this work the possibility of silanization of microstructural optical waveguides with the hollow core using (3-glycidyloxypropyl) trimethoxysilane and their further application to enzymatic immunoassay was studied.
Photonic crystal fibers with hollow core (HC PCFs) are a specific class of optical fibers characterized by microstructure with periodic holes oriented along fiber. The combination of HC PCF with Raman spectroscopy for biosensors creation is attractive in the terms of the low sample volume, the possibility to increase the integration time without sample degradation and maintaining constant focus during experiments. Here we propose layer-by-layer polyelectrolyte coating of HC PCF inner surface in order to obtain charge-selective absorption of analyte, stabilization of Surface-Enhanced Raman scattering (SERS)-active gold nanoparticles. Distance between SERS hotspots and glass reduces nonlinear signals from glass, and increases signal-to-noise ratio of SERS spectra.
Study of the penetration depth of synthesized copper nanoparticles into cut samples of human dentin was conducted. The scanning electron microscopy was used to determine the elemental composition of fresh transverse cleavage of the dentin cut for determination of the copper nanoparticles penetration with an effective antiseptic effect. The morphology of the cut surface of the dentin of a human tooth was studied and the lower limit of the diffusion boundary was determined. It was found that copper nanoparticles penetrate into the dentin cut to a depth of ~ 1.8 μm with the diffusion coefficient of 1.8×10–11 cm2/s. Despite the rather small size of the synthesized copper nanoparticles (20-80 nm), a rather small penetration depth can be explained by the high aggregation ability of copper nanoparticles, as well as the ability of a micellar solution of sodium dodecyl sulfate, in which nanoparticles were stabilized, to form conglomerates in micelles of much larger sizes.
The use of photonic crystal fibers as a basis elements for biosensor construction is a perspective trend. The advantages of this approach are the use of micro and nano volumes of samples and a significant strengthening of the analytical signal while increasing the optical path length. Quantum dots are the most promising fluorescent markers for use in the photonic crystal fibers based analysis.
The advantages of quantum dots, in this case, are associated with stability, wide range of excitation and extremely narrow range of high luminescence intensity. In this work we have investigated the behavior and optical properties of CdSe core-shell nanocrystals (quantum dots) after they including into hollow central defect of hollow core chirped photonic crystal fibers with internal surface modified by polyaniline films.
The aim of this work was the fabrication of nanolabels (SERS-nanotags) which are used for chemical analysis by means of surface-enhanced Raman spectroscopy (SERS), and registration of their SERS spectra inside photonic crystal fibers (PCF). The SERS nanotags fabrication included synthesis of silver nanoparticles with subsequent deposition of Raman active layer (thiol-group contained aromatic compound) and protecting layer composed of silica shell. Finally, SERS spectra of the SERS nanotags were registered inside PCF in order to determine the value of fiber-enhancement of the Raman signal and to estimate analytical potential of this combination.
Photonic crystal fibers (PCFs) are one of the most promising materials for biosensors construction due to their unique optical properties. The modification of PCF by noble metal nanoparticles (NPs) provides the SPR and SERS signal detection where as the application amino group-containing compounds allows efficient binding of biomolecules. In this work the internal surface of glass hollow core photonic crystal fibers (HC-PCFs) has been modified Ag and Au nanoparticles using three different approaches. PCFs were treated by: 1) mixture of NPs and precursors for silanization (tetraethoxysilane (TEOS) and (3-aminopropyl)triethoxysilane (APTES)); 2) alternately deposition of polyelectrolytes and NPs, 3) mixture of chitosan with NPs. The shift of local maxima in the HC-PCF transmission spectrum has been selected as a signal for estimating the amount of NPs on the HC-PCF inner surface. The most efficient techniques were the chitosan application for Ag NPs and silanization for Au NPs. The obtaining PCFs could be useful for creating biosensitive elements.
We introduce a sensitive method that allows one to distinguish positive and negative agglutination reactions used for blood typing and determination of Rh affinity with a high precision. The method is based on the unique properties of photonic crystal waveguides, i.e., microstructured waveguides (MSWs). The transmission spectrum of an MSW smart cuvette filled by a specific or nonspecific agglutinating serum depends on the scattering, refractive, and absorptive properties of the blood probe. This concept was proven in the course of a laboratory clinical study. The obtained ratio of the spectral-based discrimination parameter for positive and negative reactions (I+/I−) was found to be 16 for standard analysis and around 2 for used sera with a weak activity.
The advantages of microstructured fibers application to photometrical determination of positive and negative agglutination reaction is discussed. One can use this method for blood typing and determination of Rh affinity. The method is based on discrimination of the scattering properties of blood probes with a specific and a non-specific agglutinating serum.
Multiphoton microscopy (MPM) is a powerful technique for high resolution imaging of biological tissues. A specially-designed
chirped photonic crystal fiber (CPCF) is introduced for MPM applications. The CPCF eliminates most pulse
broadening effects in a broad transmission window because its cell-size radial chirp in the cladding structure localizes the
reflection of different wavelengths in different resonant layers of the cladding, similar to chirped mirrors. In contrast,
traditional hollow core fiber (HCF) consists of several identical reflective layers that produce substantial higher-order
dispersion. The feasibility of applying the CPCF for MPM imaging is studied. The propagation properties of the CPCF
are characterized by autocorrelation traces measured with and without the CPCF, which confirms an extremely low
dispersion of the CPCF. The dispersion from other optics in the MPM imaging system is further compensated by a
double-folded prism pair. In the autocorrelation trace measurement, satellite peaks are observed when the length of the
CPCF is short (~40 cm), which disappear when the fiber length is chosen sufficiently long. The satellite peaks appear to
originate from modal dispersion. With propagation lengths above 1 m, single mode propagation can be achieved in the
CPCF. The extremely low dispersion of CPCF over a wide transmission window is promising in MPM applications for
the fiber delivery of femtosecond pulses, especially in sub-20fs or tunable laser illumination.
The aspects of application of the hollow core photonic crystal waveguides for spectroscopic analysis of liquid medium
were considered. The possibility of using these structures for analysis of a fruit juice was evaluated. The principles of
processing of photonic crystal waveguide transmission spectra, which is sensitive to quality of juice, its composition, and
main component concentration, were revealed.
Possibility of photonic crystal fiber-based glucose sensor developing is discussed. We considered the concept of the use
of chirped photonic crystal fiber with big grating period as a fiber refractometer and "smart" photometric cuvette, and
possibility to combine refractometric and oxidase methods for glucose determination. Influence of refractive index
change of the liquid medium, determined by significant increase of containing glucose, to spectral characteristics of
photonic crystal fiber was studied and the optical response to insignificant change (tenths of millimoles per liter) of
glucose concentration was obtained.
We observed recent experimental results in area of photonic crystal fibers appliance. Possibility of creation of fiberbased
broadband light sources for high resolution optical coherence tomography is discussed. Using of femtosecond
pulse laser allows for generation of optical radiation with large spectral width in highly nonlinear solid core photonic
crystal fibers. Concept of exploitation of hollow core photonic crystal fibers in optical sensing is demonstrated. The use
of photonic crystal fibers as "smart cuvette" gives rise to efficiency of modern optical biomedical analysis methods.
A new type of photonic crystal fibers (PCFs) that can be used as sensitive elements of chemical and biological
sensors is presented. Hollow core photonic crystal fibers refer to a type of optical waveguides, showing
unique optical properties such as photonic band gap formation and high sensitivity for refraction index,
absorption and scattering coefficient of a medium within a hollow core. A significant influence of internal
medium scattering coefficient on a PCF's guiding properties becomes basis for design of blood typing
automatization technique specifically. Recently obtained experimental results, regarding PCF's sensitivity for
internal medium optical properties changing, are presented as well.
In this paper we show a new class of photonic crystal fiber with hollow core, with various modification of a space
lattice. We display effect of amount of layers and their locating on control of photonic band gaps in a visible band
of wavelengths. We shown influence change of refractive index of a core at filling hollow cores to various fluids on
width and a locating of photonic band gap. Such fibers unclose new opportunities for application in the capacity of
biological and chemical sensor.
We create photonic crystal optical fiber having the photonic band gap in visible range of spectrum. This fiber consists of
concentric layers of air holes of variable diameter with hollow cores. We carried out researches of their spectra of
transmission. We display influence of geometrical parameters of structure on size of the photonic band gap and its
arrangement in a visible range of wavelength. It is established, that variations of geometrical structure of fiber allow
operating size of the photonic band gap that gives unlimited opportunities guides of light.
The results of investigations of transmission properties and experimental measurements of losses in different kinds of holey fibers made from optical glass are presented. In the experiments the air-glass holey fibers with Nd-doped core and metal-doped core were used. Special attention was given to the quality of the holey fiber structure. The transmission properties were investigated at the wavelengths 0.633 μm and 1.05 μm (He- Ne laser and IFL laser, correspondingly). The losses at 1.05 μm are 0.00025 cm-1, being slightly smaller than the losses in bulk glass.
We describe the fabrication, characterization and possible application of a new type of optical material -- a 2- dimensional air-glass photonic crystal.
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